1. Technical Field
The present invention relates to public telephone stations and more specifically, to control equipment within a public telephone station that guards against a user making unauthorized telephone calls.
2. Description of the Prior Art
Public telephone improvement programs in the last decade have resulted in a multitude of telephone station innovations that serve customer needs and reduce operating costs. Illustratively, one such product is the customer-owned public telephone station. These are telephone stations that are purchased by non-telephone company customers who then lease or resell the stations.
Many services available for a telephone company-owned public telephone station are not available for the customer-owned public telephone station. For example, a telephone company-owned public telephone station operating on a charge-a-call line is provided with call screening, call blocking, call rating, and fraud protection through the telephone company's traffic service position system (TSPS) facilities for noncommercial credit card calls and through the telephone company's call processor for commerical credit card calls.
The customer owned public telephone station is usually connected to a central office via a measured business service line (1MB). This line accepts all outgoing calls and, therefore, provides greater opportunity for user fraud. To minimize the occurrence of such fraud, a restriction should be provided at some point on the measured business service line to limit the telephone calls originating at the station to those authorized by the station owner. Furthermore, when the far end party disconnects at the end of a telephone call and the user of the telephone station remains off-hook, the central office may possibly restore dial tone. Without additional protection, therefore, the user may then place a call that would be free to the user but billed to the lessor of the measured business service line.
In view of the foregoing, it is apparent that a need exists for control equipment that prevents fraudulent use of a customer-owned public telephone station.